Risk of Flooding from Surface Water
Map Llifogydd a Ddiweddarwyd ar gyfer Pecyn Sylfaenol Dŵr Arwyneb

  • English
  • wel
  • All

The surface water flood maps give an indication of the broad areas likely to be at risk of surface water flooding. This includes flooding that takes place from the surface runoff generated by rainwater (including snow and other precipitation) that: (a) is on the surface of the ground (whether or not it is moving), and (b) has not yet entered a watercourse, drainage system or public sewer. The Flood Map for Surface Water pick out natural drainage channels, rivers, low areas in floodplains, and flow paths between buildings. But it does not indicate flooding caused by local rainfall. It does not show flooding that occurs from overflowing watercourses, drainage systems or public sewers caused by catchment-wide rainfall events or river flow. A national model has been run for 1 in 30, 1 in 100 and 1 in 1000 year rainfall events. It has been modelled on a 2 metre square grid. Lead Local Flood Authorities were consulted and where available locally held model outputs have been incorporated into the maps. This dataset has been superseded by the new National Flood Hazard Maps 2019 - NRW_DS124790

Identification

Dynodydd
Identifier
NRW_DS116273
Teitl Amgen
Alternative Title
  • Surface Water Flood Risk 1000.LYR
  • Surface Water Flood Risk 100.LYR
  • Surface Water Flood Risk 30.LYR
  • Risk of Flooding from Surface Water
  • AfA375 Updated Flood Map for Surface Water Complex Package
Laith Metadata
Metadata Language
English
Lineage

The Flood Map for Surface Water is in vector (polygon) format and includes the following component layers: 1. EXTENTS - three layers showing extent of flooding for three separate probabilities : 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 2. DEPTHS - three banded layers showing depth of flooding for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 3. VELOCITY - three banded layers showing flooding velocity for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 4. HAZARDS - is the Hazard rating and is a function of depth and velocity for the particular scenario using the Hazard Rating formula HR = d x (v + 0.5) + DF where HR is hazard rating, d is depth, v is velocity and DF is a debris factor. 5. FLOW DIRECTION (25m) - three banded layers showing flood flow direction (at maximum velocity) for three separate probabilities: 1 in 30, 1 in 100 and 1 in 1000 (created from resampled 25m raster grid) 6. SUITABILITY - one layer showing basic confidence information from the modelling which gives an indication of the scale at which is it generally appropriate to use this information to assess flood risk and parameters used. This dataset is not suitable for identifying whether an individual property will flood. Because of the way they have been produced and the fact that they are indicative, the maps are not appropriate to act as the sole evidence for any specific planning or regulatory decision or assessment of risk in relation to flooding at any scale without further supporting studies or evidence.
Additional Information

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/297432/LIT_8988_0bf634.pdf

Dyddiad cyfeirnod y set ddata (Cyhoeddiad)
Dataset Reference Date (Publication)
2016-10-17
Perchennog
Owner
  Natural Resources Wales (NRW)
Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales
http://naturalresources.wales/?lang=en
Cychwynnwr
Originator
  Environment Agency Wales
Environment Agency Wales, Cambria House, 29 Newport Road, Cardiff, CF24 0TP
http://www.environment-agency.gov.uk/regions/wales
 

Extent

Extent

Hyd
Geographic Extent
Wales (WLS)
N
W
E
S
Map representing the geographic extent of the dataset


 
 

Distribution

Fformat - Math a Disgrifiad
Format Type and Description
  • Geographic Information System ( )

    Specification

    ESRI Geodatabase

 

Quality

Ansawdd Data
Data quality

Cwmpas Ansawdd
Quality Scope
Dataset
Dataset
Cydymffurfiad
Conformity
Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services
Explanation

This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
Degree
false
Lineage

The Flood Map for Surface Water is in vector (polygon) format and includes the following component layers: 1. EXTENTS - three layers showing extent of flooding for three separate probabilities : 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 2. DEPTHS - three banded layers showing depth of flooding for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 3. VELOCITY - three banded layers showing flooding velocity for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 4. HAZARDS - is the Hazard rating and is a function of depth and velocity for the particular scenario using the Hazard Rating formula HR = d x (v + 0.5) + DF where HR is hazard rating, d is depth, v is velocity and DF is a debris factor. 5. FLOW DIRECTION (25m) - three banded layers showing flood flow direction (at maximum velocity) for three separate probabilities: 1 in 30, 1 in 100 and 1 in 1000 (created from resampled 25m raster grid) 6. SUITABILITY - one layer showing basic confidence information from the modelling which gives an indication of the scale at which is it generally appropriate to use this information to assess flood risk and parameters used. This dataset is not suitable for identifying whether an individual property will flood. Because of the way they have been produced and the fact that they are indicative, the maps are not appropriate to act as the sole evidence for any specific planning or regulatory decision or assessment of risk in relation to flooding at any scale without further supporting studies or evidence.
 

Keywords

Allweddair
Keywords

GEMET - INSPIRE themes, version 1.0
Math
Type
Theme
Theme

Dyfyniad
Citation

Dyddiad (Cyhoeddiad)
Date (Publication)
2008-06-01
Code
geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme

Allweddair
Keywords

NRW Thesaurus
  • flood modelling
Math
Type
Theme
Theme

Dyfyniad
Citation

Dyddiad (Cyhoeddiad)
Date (Publication)
2024-06-19
Code
geonetwork.thesaurus.local.theme.converted_nrw-keywords

Allweddair
Keywords

IPSV Subjects List
  • Risk management
Math
Type
Theme
Theme

Dyfyniad
Citation

Dyddiad (Cyhoeddiad)
Date (Publication)
2020-11-18
Code
geonetwork.thesaurus.external.theme.subjects

Allweddair
Keywords

NRW SMNR Keywords
  • Natural Resources (Incl. Features and Processes) (SMNR)
  • Freshwater and Wetlands (SMNR)
  • Sustainable Management of Natural Resources (SMNR)
  • Management Areas (SMNR)
  • Hydrological Processes (SMNR)
  • Ecosystem (SMNR)
  • Physical Geography (Physiography) (SMNR)
  • Flooding (SMNR)
  • Soil and Land (SMNR)
  • Sea and Coast (SMNR)
Math
Type
Theme
Theme

Dyfyniad
Citation

Dyddiad (Cyhoeddiad)
Date (Publication)
2024-06-26
Code
geonetwork.thesaurus.local.theme.converted_nrw-smnr-keywords
 

Spatial Reference System

Code
British National Grid (EPSG::27700)
 

Content

Gwybodaeth Cynnwys
Content Information

Proffil CNC
NRW Profile

Elfennau CNC
Custom Elements

NRW Related Title

National Flood Hazard Maps 2019
 

Constraints

Constraints

Limitations on Public Access and Use

Math o Gyfyngiad
Restriction type
Other restrictions
Other restrictions
 

Access Constraints Directive

Limitations
no limitations
 

Access Constraints Text

Other constraints

There are no access restrictions on this data. NRW may release, publish or disseminate it freely.
 

Use Constraints

Cyfyngiadau Defnyddio
Use constraints type
Other restrictions
Other restrictions
Other constraints

© CNC/NRW and Centre for Ecology and Hydrology © NERC (CEH) Some features of this information are based on digital spatial data licensed from the Centre for Ecology and Hydrology © NERC (CEH). Defra, Met Office and DARD Rivers Agency © Crown copyright. © Cranfield University. © James Hutton Institute. Contains OS data © Crown copyright and database right 2015. Land and Property Services © Crown copyright and database right. Data may be re-used under the terms of the Open Government Licence providing it is done so, acknowledging both the source and copyright of the owners. It is the recipient's responsibility to ensure the data is fit for the intended purpose.
 
 
 

Metadata

Metadata

Dynodydd Ffeil
File Identifier
4f4c4942-4343-5764-6473-313136323733 XML
Laith Metadata
Metadata Language
English
Math o adnodd
Resource type
Dataset
Dataset
Dyddiad Metadata
Metadata Date
2025-02-04T10:44:13.148Z
Enw Safonol Metadata
Metadata Standard Name
NRW
Fersiwn Metadata
Metadata Standard Version

1.0

Pwynt Cyswllt
pointOfContact
  Natural Resources Wales (NRW)
Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales
http://naturalresources.wales/?lang=en
 
 

Publishing Body

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